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POWhy does routing break down when I modify RouteValueDictionary?
 

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  1. POWhy does routing break down when I modify RouteValueDictionary?
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    <p>I register several routes as such:</p> <pre><code>routes.MapRoute( name: "contentPage", url: "{*path}", defaults: new { controller = "ContentPage", action = "Index", path = "start" }, constraints: new { path = new NodeTypeConstraint(siteTree, "contentPage") } ); routes.MapRoute( name: "category", url: "{*path}", defaults: new { controller = "Category", action = "Index" }, constraints: new { path = new NodeTypeConstraint(siteTree, "category") } ); </code></pre> <p>And a default one:</p> <pre><code>routes.MapRoute( name: "Default", url: "{controller}/{action}/{id}", defaults: new { controller = "Home", action = "Index", Id = UrlParameter.Optional } ); </code></pre> <p>The siteTree is a tree of nodes that can be content pages, categories or products (among other things).</p> <p>In the constraint I add a new entry to the RouteValueDictionary:</p> <pre><code>public class NodeTypeConstraint : IRouteConstraint { private readonly TreeNode _siteTree; private readonly string _type; public NodeTypeConstraint(TreeNode siteTree, string type) { _siteTree = siteTree; _type = type; } public bool Match(HttpContextBase httpContext, Route route, string parameterName, RouteValueDictionary values, RouteDirection routeDirection) { var path = values[parameterName].ToString(); var node = _siteTree.Find(path); if (node != null &amp;&amp; node.Properties["type"] == _type) { values["node"] = node; return true; } return false; } } </code></pre> <p>Adding "node" to RVD lets me define actions like this one:</p> <pre><code>public class ContentPageController : Controller { public ActionResult Index(TreeNode node) { return View(node); } } </code></pre> <p>Without modifying the RVD the action would have to be:</p> <pre><code> public ActionResult Index(string path) {} </code></pre> <p>...which would force me to once again use the site tree to look up the node. I want to avoid that.</p> <p>This new helper method lets me generate links:</p> <pre><code> public static IHtmlString ActionLink(this HtmlHelper html, TreeNode node) { return html.ActionLink( node.Properties["title"] ?? node.Name, "Index", node.Properties["type"], new {path = node}, null); } </code></pre> <p>Awsome! But routing breaks down when I do "default" routing. Instead of producing a correct link the following creates a link with an empty "href" attribute:</p> <pre><code>Html.ActionLink("Register", "Register", "Account") </code></pre> <p>To fix this and without acctually knowing what the hell I'm doing, I changed the default route registration to this:</p> <pre><code> routes.MapRoute( name: "Default", url: "{controller}/{action}/{id}", defaults: new { controller = "Home", action = "Index", Id = UrlParameter.Optional }, constraints: new { id = new FakeConstraint() } ); </code></pre> <p>And this:</p> <pre><code>public class FakeConstraint : IRouteConstraint { public bool Match(HttpContextBase httpContext, Route route, string parameterName, RouteValueDictionary values, RouteDirection routeDirection) { return true; } } </code></pre> <p>I'd sleep much better if I know why MVC behaves like this. Did I go about this the wrong way?</p> <p>EDIT: If I throw out that awful FakeConstraint and instead do this, it totally works. If I only knew why, sigh.</p> <pre><code>public bool Match(HttpContextBase httpContext, Route route, string parameterName, RouteValueDictionary values, RouteDirection routeDirection) { var path = values[parameterName].ToString(); var node = _siteTree.Find(path); if (node != null &amp;&amp; node.Properties["type"] == _type) { values["node"] = node; // These two lines make FakeConstraint redundant: values["controller"] = route.Defaults["controller"]; values["action"] = route.Defaults["action"]; return true; } return false; } </code></pre>
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    1. USMarcus
    1. USMarcus
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    1. COMaybe this "default" root is present in sitetree so first or second root for some reason matches it because _siteTree.Find returns not null?
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      1. POWhy does routing break down when I modify RouteValueDictionary?
      1. USYevgeniy.Chernobrivets
    2. COBut i don't fully understand how this FakeConstraint can resolve it because it will completely ignore default route...
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      1. POWhy does routing break down when I modify RouteValueDictionary?
      1. USYevgeniy.Chernobrivets
    3. CONo it is not present in the sitetree and will not match. And yes, it's very wierd. Asp.Net mvc routing is a wierd beast.
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      1. POWhy does routing break down when I modify RouteValueDictionary?
      1. USMarcus
 

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